ML20215M283
| ML20215M283 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 05/05/1987 |
| From: | Nerses V Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20215M261 | List: |
| References | |
| NUDOCS 8705130162 | |
| Download: ML20215M283 (6) | |
Text
~.1 7590-01 UNITED STATES NUCLEAR REGULATORY COMMISSION YANKEE ATOMIC ELECTRIC COMPANY
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YANKEE NUCLEAR POWER STATION
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DOCKET NO.50-029 NOTICE OF ENVIRONMENTAL ASSESSMENT AND FINDING OF NO SIGNIFICANT IMPACT The U. S. Nuclear Regulatory Commission (the Comission) is considering issuance of an exemption from certain requirement of Appendix J to 10 CFR Part 50 to Yankee Atomic Electric Company (the licensee) for the Yankee Nuclear Power Station (Yankee) located at the licensee's site near Rowe, Massachusetts.
ENVIRONMENTAL ASSESSMENT Identification of Proposed Action:
The licensee is requesting an exemption from Paragraph III.A.3 of 10 CFR Part 50 Appendix J. " Primary Reactor Containment Leakage Testing for Water-l Cooled Power Reactors." In 1973, Appendix J was issued to establish require-i ll ments for primary containment leakage testing and incorporated by reference, ANSI N45.4-1972, " Leakage Rate Testing of Containment Structures for Nuclear
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Reactors." This Standard requires that containment leakage calculations be I
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performed by using either the point-to-point method or the total time method.
The total time method was used the most by the nuclear industry until about 1976.
As noted in N45.4, the point-to-point method is suited to uninsulated containments where atmospheric stability is affected by outside diurnal changes, 8705130162 870506 DR ADOCK 0500 9
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- while the total time method is appropriate for insulated containments that are
.relatively unaffected by diurnal changes.
In 1976, an article " Containment
. Leak Testing: Why the Mass-Plot Analysis Method is Preferred," Power Engineering, February 1976, was written which compared the results of test analyses that were performed using point-to-point, total time and mass-plot-techniques. Subsequently, the mass-plot method received the Commission's endorsement and a conforming change to Appendix J was proposed. A revision to the Standard (ntference:
ANSI /ANS 56.8-1981, " Containment System Leakage Testing") specifies the use of mass-plot, to the exclusion of the two older methods. However, at this time, licensees who wish to use mass-plot must submit an application for exemption from the Appendix J requirement that containment integrated leak rate tests will conform to N45.4. The exemption proposed by the licensee would be granted until pending changes to Appendix J become effective. The exemption applies only to the method of calculating leakage by use of mass-plot and not to any other aspect of tne tests. The mass-plot method is a newer and more accurate means of calculating containment leakage.
In the mass-plot method, the mass of air in containment is calculated and plotted as a function of time. Leakage is calculated from the slope of the Linear Least Squares.
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The Commission's staff believes that the mass-plot method was not specified in ANSI N45.4-1972 because the other more conservative methods (point-to-point and total time) were adequate and suitable for the sensitivity levels of the instrumentation in use at that time. However, with the present f
developments in technology, the mass-plot method has gained recognition as the proper one to use. The superiority of the mass-plot method becomes apparent I
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In the total time method, a series of leakage rates are calculated on the basis of air nass differences
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between an initial data point and each individual data point thereafter.
If for any reason (such as instrument error, lack of temperature equilibrium, ingassing or outgassing) the initial data point is not accurate, the results of the test will be affected.
In the point-to-point method, the leak rates are based on the mass difference between each pair of consecutive points which are then averaged to yield a single leakage rate estimate.
Mathematically, this can be shown to be the difference between the air mass at the beginning of the test and the air mass at the end of the test expressed as a percentage of the containment air mass.
It follows from the above that the point-to-point method ignores any mass readings during the test and thus the leakage rate is calculated on the basis of the difference in mass between two measurements taken at the beginning and at the end of the test, which are 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> apart.
The licensee's request for exemption and the bases therefore are contained in a letter dated April 17, 1987.
The Need for the Proposed Action: The exemption is needed to allow continued use of the mass-plot analysis method at Yankee.
Environmental Impact of the Proposed Action,: The proposed exemption will have no incremental environmental impact relative to current practice because the exemption will allow testing to be conducted in the same manner as it is currently performed.
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- ~ The erraticism of the total time method creates-a higher probability of-
. unnecessarily failing a containment integrated leakage rate test (note that the calculational; procedure is independent of containment tightness) possibly resulting in increased test frequency, critical path outage time, and exposure
.to test personnel.
Thus, radiological releases will not be greater than previously determined, nor does the proposed exemption othenvise affect radiological plant effluents, and has no other environmental impact. Therefore, the Comission concludes that there are no significant radiological or non-radiological environmental impacts associated with the proposed exemption.
Alternative to the Proposed Action:
It has been concluded that there is no measurable impact associated with the proposed exemption; any alternatives to the exemption will have either no environmental impact or greater environmental impact.
Alternative tise of Resources: This action does not involve the use of resources beyond the scope of resources used during normal plant operation.
Agencies and Persons-Consulted: The Comission's staff reviewed the licensee's request that supports the proposed exemption. The staff did not consult other agencies or persons.
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. - FINDING OF NO SIGNIFICANT IMPACT Based upon the foregoing environmental _ assessment, the Commi[sion concludes that the proposed action will not have a significant effect on the quality of the human environment. Accordingly, the Comission has determined not to prepare.an environmental impact statement for the proposed exemption.
For further details with respect to this action, see the request for exemption submittal dated April 17, 1987 which is available for public inspection at the Comission's Public Document Room,1717 H Street, N.W.,
Washington, D.C.
20555, and at the Greenfield Community College, 1 College Drive, Greenfield, Massachusetts 01301.
Dated at Bethesda, Maryland, this 8 5 day of 1987.
FOR THE NUCLEAR REGULATORY COMMISSION
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Victor Nerses, Acting Project Director Project Directorate I-3 Division of Reactor Projects I-II m
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.. FINDING OF NO SIGNIFICANT IMPACT Based upon the foregoing environmental assessment, the Connission concludes that the proposed action will not have a significant effect on the quality of the human environment.- Accordingly, the Connission has determined-not to prepare an environmental impact statement for the proposed exemption.
For further details with respect to this action, see the request for exemption submittal dated April 17, 1987 which is available for public inspection at the Connission's Public Document Room,1717 H Street, N.W.,
Washington, D.C.
20555, and at the Greenfield Community College, 1 College Drive, Greenfield, Massachusetts 01301.
~L Dated at Bethesda, Maryland, this day of 1987.
FOR THE NUCLEAR REGULATORY' COMMISSION Victor Nerses, Acting Project Director Project Directorate I-3 Division of Peactor Projects I-II
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